1. Field
The present disclosure relates generally to aircraft and, in particular, to manufacturing aircraft. Still more particularly, the present disclosure relates to a method and apparatus for spark containment at a fastener installed in a structure for an aircraft.
2. Background
In manufacturing aircraft, different parts may be connected to each other to form aircraft structures. A number of fasteners are used to assemble these structures, join these structures, or both. Thousands of fasteners are used in a single aircraft.
Oftentimes, fasteners are installed to meet various industry requirements. For instance, to minimize corrosion, fasteners may be installed such that fluids do not pass into the interior of the aircraft structure. Fasteners also may have spark protection to prevent sparking within the interior of the aircraft structure.
Spark protection is particularly important in flammable areas of the aircraft. In some instances, spark protection may be achieved using a sleeved fastener having an interference fit with the aircraft structure. This interference fit between the sleeve and the aircraft structure electrically connects the fastener system to the structure, thus providing spark protection for the fastener.
While this interference fit provides a first level of protection from sparking, aircraft regulatory agencies require a fault tolerant design in flammable areas of the aircraft. In other words, the design must take into account possible manufacturing faults. Examples of manufacturing faults include oversized holes, contamination, angled holes, burrs, or other manufacturing inconsistencies.
The presence of one of these faults may generate a spark in the hole. This sparking may produce particles that lead to undesired conditions in the aircraft. As a result, a method of spark containment, or a second level of spark protection, is required to meet agency standards.
In some cases, a cap seal is applied over the head of the sleeved fastener to achieve fault tolerance. This cap seal must be precisely and consistently applied to ensure coverage over the entire head of the fastener, as well as any inconsistent portions of the hole.
The application of cap seals to each fastener may slow the installation process more than desired. Moreover, applying cap seals to thousands of fasteners consistently may be more difficult than desired. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.